In many instances, for practical reasons, it is important to know the composition of a substance at the bottom of a container such as a tank, and because of the inaccessible location or massive size of the container, access to such "bottoms" is difficult. For example, before a tank is refilled, it may be essential to know the bottom composition because it may adversely affect the composition being introduced or the amount being charged. In the case of crude or refined liquid petroleum products, it could be of substantial economic disadvantage if the buyer believes he is purchasing a petroleum product and finds that he has purchased a significant amount of water which has settled at the bottom of the tank. Additionally, it may be important to determine whether the presence of a deleterious or unwanted "bottoms" substance is attributable to the buyer or to the seller or to the shipper. In addition to liquid sampling, it is sometimes important to obtain a sample of non-liquid substances such as a heavy petroleum residue or tar which settles at the bottom of a tank to study its composition to determine whether the product is contaminated or material introduced therein will be contaminated by the presence of such bottoms. For these and other known reasons such as those noted in U.S. Pat. No. 4,406,171 for determining the composition of tank bottoms, the present invention affords an improved and effective device for obtaining such sampling.